WELLINGTON - Prime Minister Jacinda Ardern told New Zealanders on Wednesday to behave as if they had the coronavirus and cut all physical contact outside their household when the country heads into a one-month lockdown at midnight.

Ardern declared a national state of emergency as the number of cases of COVID-19, the disease associated with the coronavirus, surged by a record 50 cases to take the national tally to 205.

The government has imposed self-isolation for everyone , with all non-essential services, schools and offices to be shut for a month from midnight (1100 GMT).

"From midnight tonight, we bunker down for four weeks to try and stop the virus in its tracks, to break the chain," Ardern told parliament.

"Make no mistake this will get worse before it gets better.

We will have a lag and cases will increase for the next week or so. Then we’ll begin to know how successful we have been."

Ardern told parliament the lockdown was triggered by early evidence of community transmission of COVID-19, the disease caused by the coronavirus.

At a news conference later in the day Ardern said modelling suggested New Zealand could have several thousands cases of COVID-19 before the numbers start coming down.

"If you have any questions about what you can or can’t do, apply a simple principle: Act like you have COVID-19," Ardern said.

"Every move you then make is a risk to someone else. That is how we must all collectively think. That’s why the joy of physically visiting other family, children, grandchildren, friends, neighbours is on hold. Because we’re all now putting each other first. And that is what we as a nation do so well."

Reuters